Actuation means for automatic slack adjusters



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B. H. BRowALl.

Filed may 6. 1931 ACTUATION MEANS FOR AUTOMATIC SLACK ADJUSTERS March 8, 1932.

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UNITED ST F i E, 1

BERT HENRY BROWALL, OF MALMO, SWEDEN, ASSIGNR TO SVENSKA AKTIEBOLAGET BROMSREGULATOR, Olk MAL-M0, SWEDEN, A CORP(')RA'TEOIQ'V OF SWEDEN" Y .eccruiirroiv MEANS rolt Anrosmmc stack nnJUsrERs Application `filed May 6, 1931, Serial No. 535,493, and in Germany February 10, 1930.

My present invention refers to an improve.- ment in actuation means'for automatic slack adjusters in brakes, especially in brakes for vehicles running on rails.v More specifically 5 the invent-lon refers to slack adjusters of the kind in which the actuation means consists of apivotally` mounted lever adapted for coaction with an abutment, and wherein a relative -movement between such parts of construction is eected at the manipulation of the brake, said abutment, point of the brake piston stroke, forming a stop to the relative movement of the lever and the abutment, and at the continuation of said stroke it performs a tilting movement of the said lever into another position, the actuation of the slack adjuster being thereby performed by means of a suitableintermediate transmis sion member.

In previously known constructions of this kind, the lever has been mounted on a pivot taking a fixed position. in relation to the under-framing ofthe car, the abutment having been mounted on the brake piston rode-.The drawback involved in this known construction is thatthere has been no mutualguiding means at handbetween the lever and the abutment, and due to the conventional freedom of lateral movement of the brake piston rod, the movement of the actuationlever is completely uncontrolled both in respect of the beginning and of the conclusion of its tilting movement, Therefore, itA has neither been possible by these means to obtain an adjustment of the brake shoe slacks according to a predetermined length of slack stroke of the brake piston, and an adjustment of this kind is generally the main object of any slack adjuster, as well known to those skilled in the art. .The

same drawback also appears if a reversed arfV rangement of the lever and the abutmentv is employed, i. e. if the lever'is mounted on a movable pivot and the abutment takes a fixed position in relation to the under-framing of the car.

Generally speaking, the aforesaid drawback is eliminated according to the invention by providing a pivotal mounting of the abutment in such a manner that it is movable transversely in relation to the direction of the at a predetermined n vtual'lateral movements of the pivot pin at the braking, sol as, at the relative movement,

always tol pass the said pivot pin at a predetermined distance therefrom. v

For this purpose it is preferredA to employ a guide in the shape ofl a slotted link surrounding the pivot pin of the lever and supporting the abutment, such slotted link being provided with; an abutment adapted to coact with the lever. y

As the position of the piston rrod in the A brake cylinder is always determined when the brake is released, it is possible by means of a longitudinal adjustment of the slotted link to determine the correct position of the abutment in order, under yall circumstances, to secure a predetermined length of the slack stroke of the brake piston, andsince the relative movement under all1 conditions is determined by the `slotted link, the movements Vof the lever 'are also completely predetermined.

ln this connection it ought perhaps to be mentioned that it has also been previously proposed to employ a slotted link guide in connection with actuation means for'slack adjusters, Ybut this slotted link has been provided with an oiiset or broken guiding slot,

and has been adapted per se. to effect the adjusting movement by meansof said oi'set or broken portion of its guiding slot. Apart from'theprincipal dierences in respect of the function of thisknown construction and the actuation means according tothe invention, the said known construction involves a plurality of disadvantages. Both the extent and the speed of the adjusting movement in relation to the movement of the brake piston are, for instance, veryV limited due to constructional considerations, and therefore these known devices cannot easily and conveniently be adapted to the different requirements appearing in separate instances.- According to the invention all of these disadvantages are also eliminated, and both the length of the lever arms and their initial and words, the bell crank lever thus guided will be tilted into the position shown in dot and dash lines in Fig, 3, and thereby the tilting of the lever arm 7 will transmit the rotating motion to the slack adjuster by means of the intermediate transmission link 8 in the manner referred to above.

ln the progress of the tilting movement de-v scribed above, the pin or roller 17 will pass through the recess 18 into the guiding slot 10 of the slotted link 9, and thereby it will prevent a return tilting movement of the Whole lever 7,13, 14 as long tinued in the same direction (towards the left in the drawings). Consequently, the movements of the lever arm 7 and the transmission link member 8 acting for the transmission of the actuation movement to the slack adjuster 6 will be positively guided in this direction. rlhe pin or roller 17 may naturally also be of a diameter so as substantially to lill up the whole guiding slot 10 in transverse direction, but a construction of such kind is by no means required in practice.

lt will be evident that since the pin or roller 17 maintains the lever arm 13 in the position shown in dot and dash lines in Fig. 3the said lever arm-at the return movement (release of the brake) cannot take a position in which it perhaps would vform an obstacle to the return movement of the piston rod bolt 3. ln other Words, the lever arm 13 will slide back while maintaining its position guided by the pin or roller 17 so that the members, when releasing the brake, will be re turned into the position shown in full lines in Fig. 3 due to the coaction with the recess 16 and the roller 15, and thereby the lever arm 7 is also tilted back for performing a repeated actuation of the slack adjuster. A specific advantage gained by employment of the pin or roller 17 is that the lever arm 13 may be made very much shorter than otherwise would have been possible, so as to eliminate the risk that said lever arm will strike the brake cylinder, or other parts of construction, at the tilting movement of the bell crank lever.

From the foregoing it will be noted thatV the distance between the abutment or roller 15 and the piston rod bolt 3 counted in the direction of length of the slotted link 9 determines the moment in which the tilting movement of the bell crank lever 7, 13, 14 takes place, or in other words for the momentin which the movement is transmitted to the slack adjuster 6. The manner of action of the slack adjuster properis to be considered to be known per se, and generally4 speaking the object of the same is to maintain a. constant amount of slack between the brake shoes and the wheels. Itis also evident that it will be possible, by means of longitudinal adjustment of the position of the slotted link 9, to control and predetermine the moment in as the movement is c onwhich thelever arm 13 strikes the roller 15 when brakinfr. Thereby it is possible to predetermine thedesired length of rstroke required for actuation of the slack adjuster and thus the length of stroke of the brake piston at the braking. Consequently, it is also possible, byan adjustment of the slotted link 9 in its direction of length, to determine the desired amount of normal slack,`and the slotted link'is preferably provided with an index 19 or the like, so that the relative positions of theconstructional parts corresponding to the desired amount of slack may be indicated and adjusted. f f vr 1 -v Naturally it is not necessary that the transmission link 8 adapted to b e-actuated by the mechanism described shall be constructed for performing a rotational movement of the movable member of the slack *.adjuster, although an actuation movement of this kind is usually employed in practice. On the contrary, the movement of the link 8 may also be utilized in the same manner for'the transmission of any other kind of movements to the slack adjuster than a rotational one', for instance a sliding movement, in case the slack adjuster is constructed so as to be actuated that way.V It is also to be noted thatthe inventionl is not limited to the shown arrangement of the parts in direct connection with the brake piston head, but that any other arrangement may be used, provided that the ac" tuation of the brake causes a corresponding relativemotion of the lever and the abutment.

l/Vhat l claim and desire to secure by Letters Patent is: i v

1. In an actuation device for automatic slack adj usters, a pivotally mounted lever means, an abutment means adapted to coaction with said lever means so as to perform a tilting movement of the latter, means for effecting a relative movement between the lever means and the abutment means when manipulating the brake, means for transmitting the tilting movement of the lever means to the movable driving member of the slack adjuster for actuating the latter, means for supporting the abutment means in a manner so that it is movable transversely to the direction of the aforesaid relative movement when braking, and a guide member connected with the abutment means and adapted to be guided trans versely in relation to the pivotal centre of the lever means so as to cause the abutment means and thesaid pivotal centre always to pass each other at a predetermined distance at their Y slack adj usters according to claim l, the additional feature that the lever means is provided With a control member, adapted to coact with the guide means for maintaining the lever means in the tilted position taken at the application 0f the` brake.

4. ln an actuation device for automatic slack adjusters according to claim 1,'the additional features that the guide means comprises a slotted link adapted to surround an extension .of the pivot bolt for the lever means; the abutment means being supported by said slottedlink; and the lever means being provided With a control member adapted to coact with the slot of the link for maintaining the lever means in the tilted position taken at the application of the brake, the slotted l link being provid-ed with a recess for permitting the entrance of the control member at the tilting of the lever means.

5. In an actuation device for automatic slack adjusters according to claim l, the additional feature that the lever means comprises a three-armed bell crank lever pivotally mounted on an extension of the piston rod bolt, one arm tof said lever being connected With the transmission means for the actuating movement to the slack adjuster, the second arm being adapted to coact With the abutment means, and the third arm being adapted to control the end positions of the Whole bellcrank lever at the tilting movement of the same. ,Y

In testimony whereof I have signed my name to this speciiication.

BERT HENRY BBCi/VALL. 

